Nato countries are scrambling for alternative routes as far afield as Belarus and Ukraine to supply their forces in Afghanistan, which are increasingly vulnerable to a resurgent Taliban, the Guardian has learned.

Four serious attacks on US and Nato supplies in Pakistan during the past month, including two in the past three days, have added to the sense of urgency to conclude pacts with former Soviet republics bordering Afghanistan to the north.

Nato is negotiating with Turkmenistan, Uzbekistan and Tajikistan to allow supplies for Nato forces, including fuel, to cross borders into Afghanistan from the north. The deal, which officials said was close to being agreed, follows an agreement with Moscow this year allowing Nato supplies to be transported by rail or road through Russia.

The deal could allow more fuel for Nato forces to be transported from refineries in Baku, Azerbaijan, and Turkmenistan. Most of the 75m gallons of fuel estimated to be used by Nato forces annually in Afghanistan comes from refineries in Pakistan.

Germany and Spain, whose troops are based in more peaceful northern Afghanistan, have negotiated separate bilateral air transport agreements with Russia.

Nato officials said yesterday that the organisation is negotiating with Ukraine and Belarus for a land route which, though long, would avoid Pakistan and the pirates of the Gulf of Aden.

The officials yesterday played down the strategic significance of Sunday's attack in Peshawar, the Pakistani town on the main transit route through the Khyber pass. But independent analysts described it as a well-planned move, with 100 militants torching more than 100 trucks.

Yesterday, in a second attack, gunmen from the Pakistani Taliban attacked a second site on the same road near Peshawar, destroying 50 containers of supplies destined for Nato forces in Afghanistan.

A week ago, another 22 trucks carrying food supplies were attacked in Peshawar. Last month, some 60 Taliban fighters hijacked a convoy of trucks travelling in daylight through the Khyber pass.

In all, 145 vehicles, trailers, containers, and two armoured personnel carriers were destroyed in Sunday's attack, according to Peshawar police.

"We have such a huge amount of material coming through, it hasn't really made a dent," one official said. "We're not short of anything because of what has happened in Pakistan." A British defence official called the attacks "militarily insignificant".

However, independent observers took a less sanguine view. Amyas Godfrey, associate fellow of the London-based Royal United Services Institute, called it a "hugely successful attack" on a soft target. It was a propaganda success which added to existing pressure on the US-Pakistan relationship, he said.

There were concerns in Washington that militants targeting supply convoys could complicate plans to put more Nato troops into the region. "It is certainly an Achilles' heel to Afghan operations, or at least a potential one," said Daniel Markey, a former state department official and a fellow at the Council on Foreign Relations.

Nato hires private contractors to carry fuel, food and other supplies to troops fighting the Taliban in Afghanistan. Most are local Pashtun businesses, so the Taliban could risk a backlash if they continue to target convoys. Pakistan is likely to face growing pressure to provide more troops to protect depots and convoys.

More than 70% of the supplies for Nato troops in Afghanistan land at the port of Karachi and are taken to Peshawar, then through the Khyber pass to Kabul.

British and Canadian troops based in the southern Afghan provinces of Helmand and Kandahar receive many of their supplies on a route from Karachi, through Quetta and across the border at the frontier town of Chaman. It is a road where travellers are vulnerable to robbers, Taliban fighters and drug runners. There are also protection rackets.

More urgent or valuable supplies to Nato forces in Afghanistan are flown in to the Bagram air base near Kabul, and the Kandahar base, which can take large C-17 transport aircraft used by the US and Britain. Hercules aircraft, the workhorse of the RAF, can also land at the British base Camp Bastion, in Helmand province.

But even with extra land routes from the north, more attacks on the overland routes to southern Afghanistan could exacerbate Nato's existing lack of "strategic airlift", UK officials said yesterday.